It’s a part of the initiation rite for acolytes.
I don't know if you saw my other post or not. I think it could be one of several events.
1. Initiation - agree. I'll put that alongside hazing.
2. Discipline - I think, at times, it is a sign to all that the offender has been disciplined. Remember Kate Spade's husband who wore a mask after she died? I think he got a reminder not to talk and was concealing his shiner. One example. Harry Reid is another (he wasn't toeing the line and got an attitude adjustment). Jimmy Carter is the latest to get an attitude adjustment and suddenly suffer TDS.
3. Promotion - This one I'm real fuzzy on. Because of the advanced age of many of the victims, I can't imagine they're just being initiated. Could it be punishment? Mebbe. But it seems to align more with promotion - perhaps initiated into higher ranks?
A sock in the eye, definitely painful, would serve as a reminder that while they're higher on the food chain (maybe literally) they're still in thrall to others.